/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Collection;
import java.util.Map;

import javax.annotation.Nullable;

import com.google.common.annotations.GwtCompatible;

/**
 * An immutable {@link ListMultimap} with reliable user-specified key and value
 * iteration order. Does not permit null keys or values.
 * 
 * <p>
 * Unlike {@link Multimaps#unmodifiableListMultimap(ListMultimap)}, which is a
 * <i>view</i> of a separate multimap which can still change, an instance of
 * {@code ImmutableListMultimap} contains its own data and will <i>never</i>
 * change. {@code ImmutableListMultimap} is convenient for
 * {@code public static final} multimaps ("constant multimaps") and also lets
 * you easily make a "defensive copy" of a multimap provided to your class by a
 * caller.
 * 
 * <p>
 * <b>Note</b>: Although this class is not final, it cannot be subclassed as it
 * has no public or protected constructors. Thus, instances of this class are
 * guaranteed to be immutable.
 * 
 * @author Jared Levy
 * @since 2010.01.04 <b>stable</b> (imported from Google Collections Library)
 */
@GwtCompatible(serializable = true)
@SuppressWarnings({ "rawtypes", "unchecked" })
public class ImmutableListMultimap<K, V> extends ImmutableMultimap<K, V>
        implements ListMultimap<K, V> {

    /** Returns the empty multimap. */
    // Casting is safe because the multimap will never hold any elements.
    public static <K, V> ImmutableListMultimap<K, V> of() {
        // BEGIN android-changed
        return (ImmutableListMultimap) EmptyImmutableListMultimap.INSTANCE;
        // END android-changed
    }

    /**
     * Returns an immutable multimap containing a single entry.
     */
    public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1) {
        ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap
                .builder();
        builder.put(k1, v1);
        return builder.build();
    }

    /**
     * Returns an immutable multimap containing the given entries, in order.
     */
    public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2) {
        ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap
                .builder();
        builder.put(k1, v1);
        builder.put(k2, v2);
        return builder.build();
    }

    /**
     * Returns an immutable multimap containing the given entries, in order.
     */
    public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2,
            K k3, V v3) {
        ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap
                .builder();
        builder.put(k1, v1);
        builder.put(k2, v2);
        builder.put(k3, v3);
        return builder.build();
    }

    /**
     * Returns an immutable multimap containing the given entries, in order.
     */
    public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2,
            K k3, V v3, K k4, V v4) {
        ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap
                .builder();
        builder.put(k1, v1);
        builder.put(k2, v2);
        builder.put(k3, v3);
        builder.put(k4, v4);
        return builder.build();
    }

    /**
     * Returns an immutable multimap containing the given entries, in order.
     */
    public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2,
            K k3, V v3, K k4, V v4, K k5, V v5) {
        ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap
                .builder();
        builder.put(k1, v1);
        builder.put(k2, v2);
        builder.put(k3, v3);
        builder.put(k4, v4);
        builder.put(k5, v5);
        return builder.build();
    }

    // looking for of() with > 5 entries? Use the builder instead.

    /**
     * Returns a new builder. The generated builder is equivalent to the builder
     * created by the {@link Builder} constructor.
     */
    public static <K, V> Builder<K, V> builder() {
        return new Builder<K, V>();
    }

    /**
     * A builder for creating immutable {@code ListMultimap} instances,
     * especially {@code public static final} multimaps ("constant multimaps").
     * Example:
     * 
     * <pre>
     * {
     *     &#064;code
     *     static final Multimap&lt;String, Integer&gt; STRING_TO_INTEGER_MULTIMAP = new ImmutableListMultimap.Builder&lt;String, Integer&gt;()
     *             .put(&quot;one&quot;, 1).putAll(&quot;several&quot;, 1, 2, 3)
     *             .putAll(&quot;many&quot;, 1, 2, 3, 4, 5).build();
     * }
     * </pre>
     * 
     * <p>
     * Builder instances can be reused - it is safe to call {@link #build}
     * multiple times to build multiple multimaps in series. Each multimap
     * contains the key-value mappings in the previously created multimaps.
     */
    public static final class Builder<K, V> extends
            ImmutableMultimap.Builder<K, V> {
        /**
         * Creates a new builder. The returned builder is equivalent to the
         * builder generated by {@link ImmutableListMultimap#builder}.
         */
        public Builder() {
        }

        /**
         * Adds a key-value mapping to the built multimap.
         */
        @Override
        public Builder<K, V> put(K key, V value) {
            super.put(key, value);
            return this;
        }

        /**
         * Stores a collection of values with the same key in the built
         * multimap.
         * 
         * @throws NullPointerException
         *             if {@code key}, {@code values}, or any element in
         *             {@code values} is null. The builder is left in an invalid
         *             state.
         */
        @Override
        public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
            super.putAll(key, values);
            return this;
        }

        /**
         * Stores an array of values with the same key in the built multimap.
         * 
         * @throws NullPointerException
         *             if the key or any value is null. The builder is left in
         *             an invalid state.
         */
        @Override
        public Builder<K, V> putAll(K key, V... values) {
            super.putAll(key, values);
            return this;
        }

        /**
         * Stores another multimap's entries in the built multimap. The
         * generated multimap's key and value orderings correspond to the
         * iteration ordering of the {@code multimap.asMap()} view, with new
         * keys and values following any existing keys and values.
         * 
         * @throws NullPointerException
         *             if any key or value in {@code multimap} is null. The
         *             builder is left in an invalid state.
         */
        @Override
        public Builder<K, V> putAll(Multimap<? extends K, ? extends V> multimap) {
            super.putAll(multimap);
            return this;
        }

        /**
         * Returns a newly-created immutable multimap.
         */
        @Override
        public ImmutableListMultimap<K, V> build() {
            return (ImmutableListMultimap<K, V>) super.build();
        }
    }

    /**
     * Returns an immutable multimap containing the same mappings as
     * {@code multimap}. The generated multimap's key and value orderings
     * correspond to the iteration ordering of the {@code multimap.asMap()}
     * view.
     * 
     * <p>
     * <b>Note:</b> Despite what the method name suggests, if {@code multimap}
     * is an {@code ImmutableListMultimap}, no copy will actually be performed,
     * and the given multimap itself will be returned.
     * 
     * @throws NullPointerException
     *             if any key or value in {@code multimap} is null
     */
    public static <K, V> ImmutableListMultimap<K, V> copyOf(
            Multimap<? extends K, ? extends V> multimap) {
        if (multimap.isEmpty()) {
            return of();
        }

        if (multimap instanceof ImmutableListMultimap) {
            // safe since multimap is not writable
            ImmutableListMultimap<K, V> kvMultimap = (ImmutableListMultimap<K, V>) multimap;
            return kvMultimap;
        }

        ImmutableMap.Builder<K, ImmutableList<V>> builder = ImmutableMap
                .builder();
        int size = 0;

        for (Map.Entry<? extends K, ? extends Collection<? extends V>> entry : multimap
                .asMap().entrySet()) {
            ImmutableList<V> list = ImmutableList.copyOf(entry.getValue());
            if (!list.isEmpty()) {
                builder.put(entry.getKey(), list);
                size += list.size();
            }
        }

        return new ImmutableListMultimap<K, V>(builder.build(), size);
    }

    ImmutableListMultimap(ImmutableMap<K, ImmutableList<V>> map, int size) {
        super(map, size);
    }

    // views

    /**
     * Returns an immutable list of the values for the given key. If no mappings
     * in the multimap have the provided key, an empty immutable list is
     * returned. The values are in the same order as the parameters used to
     * build this multimap.
     */
    @Override
    public ImmutableList<V> get(@Nullable K key) {
        // This cast is safe as its type is known in constructor.
        ImmutableList<V> list = (ImmutableList<V>) map.get(key);
        return (list == null) ? ImmutableList.<V> of() : list;
    }

    /**
     * Guaranteed to throw an exception and leave the multimap unmodified.
     * 
     * @throws UnsupportedOperationException
     *             always
     */
    @Override
    public ImmutableList<V> removeAll(Object key) {
        throw new UnsupportedOperationException();
    }

    /**
     * Guaranteed to throw an exception and leave the multimap unmodified.
     * 
     * @throws UnsupportedOperationException
     *             always
     */
    @Override
    public ImmutableList<V> replaceValues(K key, Iterable<? extends V> values) {
        throw new UnsupportedOperationException();
    }

    /**
     * @serialData number of distinct keys, and then for each distinct key: the
     *             key, the number of values for that key, and the key's values
     */
    private void writeObject(ObjectOutputStream stream) throws IOException {
        stream.defaultWriteObject();
        Serialization.writeMultimap(this, stream);
    }

    private void readObject(ObjectInputStream stream) throws IOException,
            ClassNotFoundException {
        stream.defaultReadObject();
        int keyCount = stream.readInt();
        if (keyCount < 0) {
            throw new InvalidObjectException("Invalid key count " + keyCount);
        }
        ImmutableMap.Builder<Object, ImmutableList<Object>> builder = ImmutableMap
                .builder();
        int tmpSize = 0;

        for (int i = 0; i < keyCount; i++) {
            Object key = stream.readObject();
            int valueCount = stream.readInt();
            if (valueCount <= 0) {
                throw new InvalidObjectException("Invalid value count "
                        + valueCount);
            }

            Object[] array = new Object[valueCount];
            for (int j = 0; j < valueCount; j++) {
                array[j] = stream.readObject();
            }
            builder.put(key, ImmutableList.of(array));
            tmpSize += valueCount;
        }

        ImmutableMap<Object, ImmutableList<Object>> tmpMap;
        try {
            tmpMap = builder.build();
        } catch (IllegalArgumentException e) {
            throw (InvalidObjectException) new InvalidObjectException(
                    e.getMessage()).initCause(e);
        }

        FieldSettersHolder.MAP_FIELD_SETTER.set(this, tmpMap);
        FieldSettersHolder.SIZE_FIELD_SETTER.set(this, tmpSize);
    }

    private static final long serialVersionUID = 0;
}
